1. Field of the Invention
This invention relates generally to fusers used in the electrophotographic process, and more particularly to a pressure roll cleaner for removing residue from the surface of a pressure roll.
2. Description of the Related Art
The basic xerographic process comprises exposing a charged photoconductive member to a light image of an original document. The irradiated areas of the photoconductive surface are discharged to record an electrostatic latent image corresponding to the original document. A development system moves a developer mix of carrier granules and toner particles into contact with the photoconductor surface. The toner particles are attracted electrostatically from the carrier granules to the latent image forming a toner powder image thereon. The toner powder image is then transferred to a sheet of paper or other support material. This sheet of paper advances to a fuser which permanently affixes the toner powder image to the paper.
The fuser generally comprises a fuser roll, a pressure roll, and an oiling system. The fuser and pressure rolls each have circumferential surfaces in contact with each other. Toner powder is affixed to the paper as the paper passes through a nip between the fuser roll and the pressure roll.
The oiling system applies oil to the surface of the fuser roll for lubrication. As the fuser roll contacts the pressure roll, a portion of the oil on the surface of the fuser roll is transferred to the surface of the pressure roll. Similarly, the fuser roll surface will contain other contaminants such as residual toner powder and paper fibers which are also transferred to the surface of the pressure roll. The oil and other contaminants must be removed from the surface of the pressure roll to prevent this residue from being transferred to the paper as it passes through the nip between the fuser roll and pressure roll. If not, this residue will form a copy quality defect on the paper. As a result, it is desirable to provide an apparatus for removing the residue from the circumferential surface of the pressure roll.
In an attempt to clean the circumferential surface of the pressure roll, a pressure roll cleaner 100, as shown in FIG. 6, was added to the fuser assembly. The conventional pressure roll cleaner 100 consisted of a sheet 11 of absorbent material having a front surface 101 in contact with the surface of the pressure roll. The edges 102 of the absorbent sheet 11 were folded over and stitched to a back surface 103. The pockets between the folded-over edges 102 and seams 104 formed by the stitches received support rods 20, 21 which held the pressure roll cleaner 100 in contact with the pressure roll. An area on the front surface 101 between the two seams 104 of the pressure roll cleaner 100 formed a cleaning surface which collected residue while the pressure roll rotated.
One of the main problems with the conventional pressure roll cleaner 100 was its short user life. Once the front surface 101 became saturated with residual oil and other contaminants, the conventional pressure roll cleaner 100 was discarded and replaced with a new one. The back surface 103 could not be used as a cleaning surface since the folded-over edges 102 formed an irregular surface unsuitable for cleaning. Furthermore, the location of the two seams 104 limited the cleaning area on the front surface 101. The two seams 104 increased the stiffness of the absorbent sheet at these locations, which resulted in inefficient contact with the pressure roll. As a result, the absorbent sheet 11 could not collect residue at areas near the seams 104.
Due to these drawbacks, the conventional pressure roll cleaner had to be replaced frequently (approximately 6-9 times per 1 million prints). The costs associated with the frequent maintenance for replacing the used pressure roll cleaners and the costs associated with stockpiling sufficient numbers of replacement pressure roll cleaners made the design of the conventional pressure roll cleaner undesirable.
The asymmetrical design of the conventional pressure roll cleaner was also disadvantageous if installed improperly. For example, if a user inadvertently installed the conventional pressure roll cleaner with the back surface 103 facing the circumferential surface of the pressure roll, ineffective cleaning would occur and further maintenance would be necessary to reinstall the pressure roll cleaner properly.